High molecular weight, water insoluble vinyl pyrrolidone/acrylic acid (VP/AA) copolymers are important coating and textile sizing agents which are compatible with monovalent inorganic salts, plasticizers and many soluble gums and resins and which possess excellent moisture resistance. These copolymers are also useful in adhesive formulations and display good anti-deposition properties for reduced soiling of textiles. Additionally, hard, transparent films of these copolymers can be cast for use in photographics or as water proof coatings on paper, metal, textile and plastic surfaces.
Notwithstanding these valuable properties, the utility of VP/AA copolymers has been somewhat limited due to complications encountered in coating operations which derive from their insolubility both in water and in alcohol. Previously, in order to form VP/AA copolymer solutions, it has been the practice to neutralize the copolymer, thus destroying its anionic property, which is responsible for hydrogen bonding and many of the above advantages, or to employ a high boiling solvent, such as dimethyl formamide, N-methyl pyrrolidone, dimethyl acetamide and others. However, such high boiling compounds are impractical for applications involving paper, textiles and many plastics which cannot tolerate the high temperature needed for solvent removal.
Accordingly, it is an object of the present invention to overcome the above difficulties and to extend the utility of VP/AA copolymers to applications involving paper, textiles, plastics and other uses.
Another object of this invention is to provide a low boiling solubilizing agent for VP/AA copolymers having weight average molecular weight of between about 5,000 and 400,000.
These and other objects of the invention will become apparent from the following description and disclosure.